Myth about heat loss from your head.

We've all heard the statement that the majority of heat loss is from our heads. This is inaccurate. The truth is the more skin exposed to cold air then the more heat loss will occur.

You will have more heat loss from an exposed torso than an exposed head. So if you are stranded buck naked in a blizzard and have the choice to cover yourself with either a head stocking or a coat then choosing the coat will have less heat loss than if you took the stocking.

However, the blood capillaries are closer to the skin surface in your head than the majority of your bed - this is why it feels like heat is escaping from you body in cold weather without a hat. Here in Colorado many people in the winter, on a sunny day without wind, can feel warm with a hat and only a tee shirt on their torso. However they would be better served to put a coat over the tee shirt and forego the hat. But they may feel colder due to how close the capillaries in the head are to the surface. Of course it would be best if they wore both a hat and a coat.

Let's correct ourselves and stop saying the majority of heat loss is from our heads - it is medically inaccurate.

meh. Most people in cold weather, including the soldiers in the original study, wear clothes when it is cold; they even wear boots and shoes and gloves (my gosh). Soldiers were required to be clean shaven with closely cropped hair (one respones to lice and typhus). However, outside of combat, not too many like to wear helmets (and the winter helmet liners). Indeed many poeple, soldiers or not like to go bareheaded much of the time. With vigorous exercise in the winter, usuallly the first area to be exposed is the head (people take their hats off; I wear a well ventilated climbing helmet in the backcountry), it helps cool the body and reduce fogging of glasses. So, YES, in the winter most people lose most of the heat they close through the well-vascularized surfaces of the head and neck because they are generally fully clothed, gloved, and shoed, usually with pretty effective materials. To avoid loss of this heat when not active, put on a hat or a balaclava. Sheesh.

always heard it wasn't the issues of size of exposure etc. Heard the body will not shut down blood flow to the head, despite loss of heat, like the body will shut down blood flow to legs/arms etc. Thus the body will keep on losing heat via the head, DON'T know the truth of all that, but was told it multiple times :)

Allow me to play devil's advocate for a minute here. All you did was start a thread and say "no, that thing that you think isn't true, stop thinking that." Got anything to back it up? Any sort of data or, well, anything that supports your statement? Or are we just supposed to trust you?

always heard it wasn't the issues of size of exposure etc. Heard the body will not shut down blood flow to the head, despite loss of heat, like the body will shut down blood flow to legs/arms etc. Thus the body will keep on losing heat via the head, DON'T know the truth of all that, but was told it multiple times :)

Correct--head and heart; extremities vasconstrict; also torso, arms, & legs generally have some fat that works as an insulator--hands, feet, nose, ears more susceptible to frostbite (and heat loss but, lots of reduced blood/heat flow to hands and feet; face is highly vascularized--lots of blood flow/heat loss.

Allow me to play devil's advocate for a minute here. All you did was start a thread and say "no, that thing that you think isn't true, stop thinking that." Got anything to back it up? Any sort of data or, well, anything that supports your statement? Or are we just supposed to trust you?

Ha ha, I always wondered where my dad got that. Every time we were going out in the cold he would say "wear a hat; you know xx% of your heat is lost through your head." (the xx would be different every time). I always chuckled, but wearing a hat in the cold is still good advice, no matter what the percentage is.

So call it 9% of adult body surface is head. But the assumption that's nicely proportionate to actual heat loss, which appeals to those who need to simplify things, including some guys of unclear scientific credentials at a "center for science policy" is just as wrong as the 50% figure. Actually, more wrong.

Subcutaneous fat and muscle distribution accounts for a lot of insulation. We have relatively little of either on our heads, which are richly vascularized. And head and face skin's full of sweat glands, which carry away heat through insensible perspiration.

So actual contribution to heat loss - or gain - by the head is considerably greater than 9% After you also adjust for the head being higher up and more exposed to convective cooling from airflow, probably 1/5 of all heat loss. And can exceed 1/4 in children, who have disproportionately larger heads.

By contrast, we have a bunch of fat and muscle on our trunks. In general, the upper back is the most important part of the body for retaining heat; Stegman showed that the back muscles fill with blood and create a sort of blanket over the rear of the heart and lungs, where core heat production collides with incoming cold air. So even though our arms and legs have a lot more surface area, relatively speaking, the reason vests keep us warm is that they further insulate the upper back.

And legs also have a thing called counter-current circulation, which evolved in vertebrates to reduce cold damage risk in lower extremities. Reason birds can perch on a leg in the north atlantic and not get frostbite. Our hands have some of that too. We also habituate to cold in our lower limbs better than to our heads; meaning we don't feel it as much. Same idea; we evolved to have bare legs and feet in variable climates. This is why, incidentally, we see people during January thaws walking around in shorts when it's 40. Or women walking around in heels and short skirts when it's 25. We just don't feel it the same way.

So bottom line: most of these science policy folks' fundamental premises are wrong. But it's a cute idea, along with then proceeding to query sugar and kids' behavior: Replace those myths with even more problematic reasoning.

The Army's old model isn't unreasonable in any case, it just assumes we aren't living naked in a cold box with thermocouples up our ass. Take an extreme case of the Inuit; prolly 3/4 of their heat loss is from the face. The rest is covered so well they needed to invent vented parkas to let out the warm humid air during work. So is it a myth to say that most their heat loss is from the head?

Whereas partly naked peeps at football games do fine because a) they're so drunk. Which keeps them from feeling pain, and also turns into excess calories rapidly and also vasodilates to boot, so their skin feels toasty even as they lose core heat, b) the crowd around them actually creates a microenvironment that's a lot warmer and with less moving air than even a few feet above their heads, and c) they can get away with it as long as the air is dry and cold. If it starts to snow, and their skin gets wet, it's bye bye or the ER.

So we're good to go with the bikinis and wearing a hat since they'll be surrounded by shirtless dudes pouring out heat from their core and breathing warm air heavily on them. As long as it doesn't snow.

Curious about the kids and sugar studies. Are those like the eating nuts studies? I'm using studies but maybe that's the wrong word.